1. Field of the Invention
The present invention relates to the inspection of marine vessels such as barges, bulk carriers, and tankers and particularly the underdeck structure including the beams, girders, welds, and stiffeners. Even more particularly, the present invention relates to an improved method of video inspection for barges, ships, and other marine vessels, that employs video imaging, preferably a digital video camera and a high resolution telephoto-magnifying lens that scans an area (such as a suspect area) of a vessel, such as for example the underdeck area of a barge.
2. General Background of the Invention
The inspection of marine vessels such as barges and ships requires that an inspector be within about 24 inches (about 61 cm) of the area to be inspected so that any cracks flaws, corrosion or pitting can be observed in welds, beams, girders, stringers and other structural members. This presents a problem for inspection of under deck areas of very large vessels because the underdeck area can be a long distance away from any floor or like supporting surface that could be occupied by an inspector.
To provide for inspection of under deck areas of barges, bulk carriers, and tankers, the owner is typically required “stage out” the cargo hold so that the surveyor or inspector can be placed very close to the structure being inspected. This can be a very expensive proposition costing hundreds of thousands of dollars for a very large vessel such as a four hundred foot (120 m) ship or a five hundred foot (150 m) barge.
Patents have issued that discuss video inspection using digital video cameras and a telephoto lens. The Offerhause et al. patent, U.S. Pat. No. 5,567,273, entitled “Method of Reducing Surface Irregularities in Paper Machine Head Box Components” discussed video inspection of hole inlet radii to provide further evidence of non-uniformities related to streak locations. A digital video camera inspection technique is discussed using CCD (Charged Coupled Device) technology to obtain distortion free images of superior quality and resolution. Halogen “broom” lighting is provided in order to give clear contrast and a telephoto lens to ensure a flat image. The images are then digitized for detailed computer analysis to an accuracy of 0.1 millimeters (0.004 inch), in a manner similar to using an optical comparator. This technique was said to be useful for inspection of the apron floor joint, turbulence generator perforated plate, and inlet tube bank. Offerhause is not directed to long distance inspection of marine vessels.
The Mueller patent, U.S. Pat. No. 5,508,735, entitled “Underdeck Inspection Device” relates to an apparatus and method for the remote visualization and inspection of an internal storage space, such as a ship's hold. The apparatus includes a mounting stand to which is rotationally mounted a support shaft, the support shaft having a camera and a light source secured thereto. The camera and light source rotate with the support shaft, and are pivotally movable relative to the support shaft. A drive shaft extends through the support shaft and is operable to simultaneously pivot the light source camera. A light adjustment drive shaft is mounted to the hollow support shaft and allows the operator to pivot the light source independently of the camera to permit a wider field of view than would otherwise be available. The apparatus is inserted, via an exterior access opening, into a storage space and thereafter operated to allow an inspector, located outside of the storage space, to visually inspect the surfaces surrounding and defining the storage space. The Mueller device does not cover many areas (and is therefore unacceptable) because it rotates about a fixed center. It is only functional from the outside of the tank.
A stereo microscopic inspection system that employs a telephoto objective assembly is the subject of U.S. Pat. No. 4,824,228.
Electronic video dental cameras that employ telephoto lenses are disclosed in U.S. Pat. Nos. 5,016,098; 5,115,307; 5,251,025; and 5,429,502. Other patents that discuss the use of a telephoto lens with a video camera include U.S. Pat. Nos. 5,808,810; 5,572,277; 5,543,840; 5,515,206; 5,479,203; 5,420,632; 5,290,168; 5,285,317; and 5,260,834.
The following U.S. patents were cited in a corresponding U.S. patent application: Strait et al (U.S. Pat. No. 5,355,818), Chang et al (U.S. Pat. No. 4,750,035), Minami (U.S. Pat. No. 5,905,595), Jones (U.S. Pat. No. 6,301,371), McDonald (U.S. Pat. No. 6,401,983) and Levine (U.S. Pat. No. 3,780,224).